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Basic Optical Fiber Nonlinear Limits
Published in Andrew Ellis, Mariia Sorokina, Optical Communication Systems, 2019
Mohammad Ahmad Zaki Al-Khateeb, Abdallah Ali, Andrew Ellis
Figure 2.1a shows a single span optical transmission system that deploy two types of optical fiber: non-zero dispersion shifted fiber (NZDSP) and standard single-mode fiber (SSMF). Two CW lasers (the power of each one is 0 dBm) were transmitted through the span, and the spectral separation between the two CWs changes to observe the effect of phase mismatching on the power Kerr nonlinear product generated by the end of the fiber, as shown in Fig. 2.1b. The figure shows that XPM power has the highest value at strongly phase-matched mixing components (low frequency separation, Δβ → 0) for both types of fiber. As the frequency separation between CWs increases, the growth of phase mismatching Δβ between the CWs causes a degradation in the XPM product power which can be analytically concluded from the second term in Eq. 2.3. At weakly phase-matched regime (Δβ ≫ 0), the XPM power shows lower degradation slope in NZDSF (compared to SSMF) due to the fact that it has lower dispersion value (lower phase mismatch growth rate).
Basic nonlinear fiber optics
Published in Kuppuswamy Porsezian, Ramanathan Ganapathy, Odyssey of Light in Nonlinear Optical Fibers, 2017
XPM induced intensity interference can be studied by simultaneously propagating an intensity modulated pump signal and a continuous wave probe signal at a different wavelength. The intensity modulated signal will induce phase modulation on the cw probe signal and the dispersion of the medium will convert the phase modulation to intensity modulation of the probe. Thus the magnitude of the intensity fluctuation of the probe signal serves as an estimate of the XPM induced interference. Figure 1.6 shows the intensity fluctuations on a probe signal at 1550 nm induced by a modulated pump for a channel separation of 0.6 nm. Figure 1.7 shows the variation of the RMS value of probe intensity modulation with the wavelength separation between the intensity modulated signal and the probe. The experiment has been performed over four amplified spans of 80 km of standard single-mode fiber (SMF) and non-zero dispersion shifted fiber (NZDSF). The large dispersion in SMF has been compensated using dispersion compensating chirped gratings. The probe modulation in the case of SMF decreases approximately linearly with 1/∆λ for all ∆λs; the modulation is independent of ∆λ. This is consistent with the earlier discussion in terms of Lwo and Leff.
Flexi-Grid Technology
Published in Ashish Raman, Deep Shekhar, Naveen Kumar, Sub-Micron Semiconductor Devices, 2022
Divya Sharma, Shivam Singh, Anurag Upadhyay, Sofyan A. Taya
In 2009, Salsi et al. successfully transmitted a Nyquist-WDM superchannel of 10 × 112 Gb/s PM-QPSK channels with very narrow spacing = 1.1 × symbol rate. They observed coverage distances of 3300, 2300, 1120, and 800 km, respectively, by employing pure silica core fiber (PSCF), large effective area fiber (LEAF), SSMF, and non-zero dispersion shifted fiber (NZDSF) at a BER 3 × 10−3. The experiment work is accomplished using EDFA amplification, a Nyquist optical filter, and RFS [31].
Experimental investigation of VCSEL-based optical heterodyning with PAM 4 and envelop detection for 5G fronthaul systems
Published in Journal of Modern Optics, 2022
R. S. Karembera, K. Nfanyana, G. M. Isoe, T. B. Gibbon
We performed a radio-over-fiber (RoF) transmission of a photonically generated 10-GHz PAM-4 RF carrier signal using the setup of Figure 4. To act as the baseline for system performance evaluation, we initially performed an 8.5-Gbps on-off keying (OOK) data modulation without optical heterodyning. A Mach–Zehnder modulator (MZM) was used to modulate VCSEL 1 with the 8.5-Gbps data. The 8.5-Gbps binary data was received from the N channel of the PPG when the switch of Figure 4 was at position 1. The modulated single optical signal from VCSEL 1 was transmitted and received after 24-km of non-zero dispersion shifted fiber (NZ-DSF) before detected by a 12.1-GHz photo detector as shown in Figure 4. During the second step to photonically generate a modulated 10-GHz RF carrier signal, the modulated VCSEL 1 was coupled with VCSEL 2 as shown in Figure 4. The photonically generated and modulated RF signal was transmitted over the same 24-km NZ-DSF to the PD. In this second step, after the PD, a low-noise linear electrical amplifier (EA) was used to amplify the received photonically generated and modulated RF carrier signal. An electrical mixer was used to down-convert the 10-GHz RF carrier to an IF of 4 GHz. This was achieved when a signal generator was used to generate a 6-GHz RF local oscillator (LO) signal to the LO port of the mixer. The output of the electrical mixer was then recorded by an oscilloscope for offline signal processing.